A cathodically protected natural gas pipeline experienced an external corrosion failure in its eleventh year of service. The pipeline exhibited high levels of induced AC voltage as a result of being parallelled by high-voltage powerlines, with the failure occurring at a location of peak AC voltage. An investigation uncovered additional corrosion pits, and it was concluded that these pits, as well as the failure, were caused by AC corrosion.

An AC mitigation system was designed to reduce the steady-state AC voltages to levels that would minimize the risk of subsequent AC corrosion damage, as well as reduce the electrical shock hazards faced by pipeline personnel and the general public. An investigation of fault current effects was not included as part of this project,

Subject
Holidays, Piping, Voltage, Cathodic protection, Magnesium anodes, Pipelines, Wiring, Soil resistivity, Current densities, Mechanical failure, Alternating current corrosion, Electrodes, Soil
Keywords:
induced AC voltage, AC corrosion, AC mitigation, pipeline corrosion, corrosion failure, magnesium anode consumption rates
© 2004 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2004
Association for Materials Protection and Performance (AMPP)
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